Concurrent transaction processing in a high performance distributed system of record

ABSTRACT

A distributed ledger and transaction computing network fabric over which large numbers of transactions are processed concurrently in a scalable, reliable, secure and efficient manner. The computing network fabric or “core” is configured to support a distributed blockchain network that organizes data in a manner that allows communication, processing and storage of blocks of the chain to be performed concurrently, with little synchronization, at very high performance and low latency, even when the transactions themselves originate from distant sources. This data organization relies on segmenting a transaction space within autonomous but cooperating computing nodes that are configured as a processing mesh. The nodes operate on blocks independently from one another while still maintaining a consistent and logically-complete view of the blockchain as a whole. Safe and performant transaction processing is provided using an optimistic concurrently control that includes a collision detection and undo mechanism.

BACKGROUND Technical Field

This application relates generally to managing a distributed system ofrecord across a set of computing resources in a distributed network.

Brief Description of the Related Art

Distributed computer systems are well-known in the prior art. One suchdistributed computer system is a “content delivery network” (CDN) or“overlay network” that is operated and managed by a service provider.The service provider typically provides the content delivery service onbehalf of third parties (customers) who use the service provider'sshared infrastructure. A distributed system of this type typicallyrefers to a collection of autonomous computers linked by a network ornetworks, together with the software, systems, protocols and techniquesdesigned to facilitate various services, such as content delivery, webapplication acceleration, or other support of outsourced origin siteinfrastructure. A CDN service provider typically provides servicedelivery through digital properties (such as a website), which areprovisioned in a customer portal and then deployed to the network.

A blockchain is a continuously growing list of records, called blocks,which are linked and secured using cryptography. Each block typicallycontains a cryptographic hash linking it to a previous block, andtransaction data. For use as a distributed ledger, a blockchaintypically is managed by a peer-to-peer network collectively adhering toa protocol for validating new blocks. Once recorded, the data in anygiven block cannot be altered retroactively without the alteration ofall subsequent blocks, which requires collusion of the network majority.Blockchains are suitable for the recording of events, various recordsmanagement activities (such as identity management, transactionprocessing, documenting provenance, etc.) and others. Generalizing, ablockchain is a decentralized, distributed and digital ledger that isused to record transactions across many computers so that the recordcannot be altered retroactively without the alteration of all subsequentblocks and the collusion of the network. In a typical blockchain, blockshold batches of valid transactions that are hashed and encoded into adata structure. In this structure, and as noted above, each blockincludes the cryptographic hash linking it to the prior block in theblockchain. The linked blocks form a chain. This iterative processconfirms the integrity of the previous block, all the way back to theoriginal genesis (or first) block.

Traditional blockchain implementations treat the blockchain as a simplesequence of blocks. Such approaches severely limit the achievableperformance of blockchain implementations, typically by creatingbottlenecks in processing, communicating and storing the blockchain inits aggregate form.

BRIEF SUMMARY

This disclosure provides for a high performance distributed ledger andtransaction computing network fabric over which large numbers oftransactions (involving the transformation, conversion or transfer ofinformation or value) are processed concurrently in a scalable,reliable, secure and efficient manner. In one embodiment, the computingnetwork fabric or “core” is configured to support a distributedblockchain network that organizes data of the blockchain in a mannerthat allows communication, processing and storage of blocks of the chainto be performed concurrently, with little synchronization, at very highperformance and low latency, even when the transactions themselvesoriginate from remote sources. This data organization relies onsegmenting a transaction space within autonomous but cooperatingcomputing nodes that are configured as a processing mesh. Each computingnode typically is functionally-equivalent to all other nodes in thecore, and preferably each node can carry the entire load of the system.A computing node typically comprises a cluster of computing,communications and storage elements. More generally, all computing nodesthat comprise the core network preferably are considered to be equal toone another, and no individual node, standing alone, is deemed to betrustworthy. Further, with respect to one another, the nodes operateautonomously, and preferably no node can control another node. The nodesoperate on blocks independently from one another while still maintaininga consistent and logically complete view of the blockchain as a whole.

The performance distributed system of record preferably separates theUnspent Transaction Output (UTXO) database from the transactionprocessing, with the UTXO space being partitioned across multiple UTXOhandlers The resulting data organization promotes increased concurrentprocessing with decreased synchronization, thereby resulting in a systemwith higher transaction throughput and lower transaction processingtimes. According to another feature, safe and performant transactionprocessing given this concurrent processing structure is provided usingan optimistic concurrently control that includes a collision detectionand undo mechanism.

The foregoing has outlined some of the more pertinent features of thesubject matter. These features should be construed to be merelyillustrative. Many other beneficial results can be attained by applyingthe disclosed subject matter in a different manner or by modifying thesubject matter as will be described.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the subject matter and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating a networking architecture thatprovides a distributed system of record with transactions organized intoa blockchain according to this disclosure;

FIG. 2 depicts a block segmentation according to the technique herein;

FIG. 3 depicts a segmented blockchain;

FIG. 4 depicts a segment migration and reassignment process;

FIG. 5 depicts an inter-node segment handling process of thisdisclosure;

FIG. 6A depicts a representative computing node block diagram and itsoperation while performing transaction validation;

FIG. 6B depicts the computing node of FIG. 6A and its operation whileperforming block mining and verification;

FIG. 7 is a high level depiction of a concurrent processing technique ofthis disclosure;

FIG. 8 is a detailed depiction of the operations that are carried outamong various nodes and node elements to provide streaming blockgeneration, transmission and validation according to this disclosure;

FIG. 9 depicts a content delivery network (CDN) architecture that may beassociated with the computing network fabric; and

FIG. 10 depicts a representative machine configuration;

FIG. 11 depicts a representative configuration of transaction and UTXOhandlers to facilitate concurrent transaction processing according tothis disclosure;

FIG. 12 depicts a representative transaction dialog between atransaction handler and a UTXO handler;

FIG. 13 depicts a representative dialog of a failed transaction;

FIG. 14 depicts a representative dialog of a race condition; and

FIG. 15 depicts a representative dialog of reversing a failedtransaction according to the technique of this disclosure.

DETAILED DESCRIPTION Overall High Level Design

FIG. 1 depicts a scalable, high performance architecture forimplementing a distributed system of record with transactions organizedinto a blockchain. At a high level, the system is divided into multiplefunctional areas as shown, namely, a periphery 100 a, an edge 100 b, anda core 100 c. The system may comprise other functional areas tofacilitate delivery, administration, operations, management,configuration, analytics, and the like, but for simplicity these areasare not depicted. As used herein, the periphery 100 a refers generallyto elements associated with a boundary 101. These elements typicallyinclude client-server based electronic wallets or wallet devices,terminal and point of sale devices, legacy financial network elementsand associated adapters. Generally, and as used herein, any elementinvolved with creating and consuming transactions including, withoutlimitation, financial transactions, may be an element in the periphery101. The periphery may extend globally. The edge 100 b typically refersto the elements of an overlay network associated with boundary 102.Representative elements include, without limitation, the processing,communication and storage elements (edge servers, switches/routers,disks/SSDs) running on an overlay edge network (e.g., a CDN such as)Akamai®). A CDN such as described advantageously provides low latencypoints of presence (relative to the end users/devices) that aggregateand, as will be described, route requested transactions and theirassociated results (to and from elements in the periphery) efficiently.Wallet services may be located within the edge. The edge elements alsoact individually, collectively, and in conjunction with other servicesas a security perimeter protecting the core 100 c from attacks and otheradversarial activity. While a CDN-specific implementation is preferred,a typical edge network in the system herein need not be limited to a CDNedge network. Any suitable network, new or extant, could be usedincluding, without limitation, cloud-based systems.

The core 100 c refers to elements associated with boundary 103. As willbe described, preferably the core 100 c is a high performance network ofnodes that together support the processing and storage of transactionblockchain(s) meeting specified performance requirements including, butnot limited to, throughput, response time, security and data integrity.A node (sometimes referred to as a “computing node”) in this contexttypically is a cluster of computing, communications, and storageelements. More generally, a cluster as used herein refers to one ormore, and possibly many, computing, communications, and storageelements. In one embodiment, the core 100 c comprises overlay networknodes, although this is not a requirement, as the core 100 c maycomprise a set of nodes distinct from the CDN and dedicated to the coreoperations (as will be described). Typically, computing nodes areinterconnected by network transits and have a high degree ofinterconnectivity to reduce or eliminate topological bottlenecks.

To facilitate high performance, preferably the core network isconstructed using a high quality, high capacity, and diverseinterconnect. The particular configuration of the core network typicallyis implementation-dependent, at least in part based on the nature of theconsensus protocol that is implemented in the blockchain. Depending onthe consensus protocol used, the size of the core network (and/or thedistribution of various computing nodes therein) may also be constrainedas necessary to ensure sufficiently low latency network communicationsacross the core.

In one non-limiting implementation, the CDN edge 100 b supports aglobally-based service having associated therewith a core network 100 c(e.g., that is located across a plurality of networked data centers in agiven geography).

Referring again to FIG. 1, message 104 is an example of a device (e.g.,an end user device, an electronic wallet, etc.) sending a transactionrequest to an edge server (e.g., such as a CDN edge server). It shouldbe appreciated that a multitude of such messages (and that will be sentto and processed by the core network as described herein) are expectedto originate from server, devices, and wallets worldwide. The messagesmay be transmitted over persistent connection or ephemeral connections,as well as via new or extant networks where those networks may be partof legacy or network infrastructure purpose built to natively supportthe system capabilities described herein. Further, messages may be sentto one or more edge servers to reduce reliance on any single point ofingress to the system.

Message 105 is an example of an edge element routing transactions(possibly including the one contained in message 104) to an appropriateelement in a core node 110 (a set of which nodes 110 are depicted). Fora given transaction there may be multiple messages 105 that route thesame transaction or a hash (or other digest) of the same transaction tothe appropriate element in other core nodes. It is not required that allmessages 105 contain a full representation of a transaction. A digest ofa transaction may be transmitted (1) to make core elements aware of theexistence of a transaction, and (2) to provide a robust way to check theintegrity of messages containing full transactions. This enablescomplete, yet efficient, propagation of incoming transaction messages tothe appropriate elements in all core nodes. It also greatly reduces thenetwork loading associated with traditional gossip protocols and yetprovides protection, e.g., from compromised edge elements censoring orcorrupting transactions.

Message 106 is an example of a core node element routing transactions tothe appropriate element in another core node. There may be multiplemessages 106, such that a core node element participates in propagatingtransactions or transaction digests across the core nodes of the system.Core nodes receiving message 106 may, in turn, generate other messages106, further propagating the messages across the core nodes of thesystem.

Topology-Aware Data Propagation

While any data propagation protocol may be employed, one preferredapproach herein is to improve upon cost and latency of traditionalrandomized peer-to-peer gossip protocols by shaping the propagation tothe underlying network topology. In concert, messages 104, 105, and 106comprise paths of propagation starting with topologically most proximateelements and reaching topologically less- or least-proximate elements. Adevice that sends messages 104 to other edge elements typically followsdifferent paths of propagation across the network. This is illustratedby the messages 107, 108, and 109 propagating in a different direction.Further, the path of propagation starting from a given device, ingeneral, may change over time to achieve proper load balancing andsecurity.

Service Discovery and High Performance Mapping

Again referring to FIG. 1, before any messages are sent, each elementoriginating a message typically must discover the address of thereceiving element. An address may be an Internet Protocol (IP) addressor some other name or number in an address space in some type of network(e.g., peer-to-peer network or overlay network). Discovering the addressof another element can be achieved in a variety of ways but generallyinvolves sending a set of element attributes to a discovery service andreceiving address information in return. In one embodiment that ispreferred, the attributes of the system elements to be discovered areencoded as domain names, thereby allowing the system to use a CDN's highperformance domain name lookup services to return the necessary addressinformation. Using an overlay network's mapping technology offersseveral advantages. It supports large domain name spaces to enable eventhe largest scale deployments. This enables an edge element, forexample, to route transactions not just to a core node, but even tospecific elements in the core node that handles the associated portionsof the transactions' identifier space. This same type of fine-grainedrouting can be done for communications between core node elements; inparticular, and using CDN DNS services, an element in one node handlinga set of segments, partitions, or other groupings of transactioninformation can send messages directly to elements in other core nodesthat handle the same segments, partitions, or other groupings oftransaction information. This is advantageous because although trafficmay traverse a common set of low level network routers/switches, thecore nodes need not inspect and route each transaction individually. Theuse of the CDN name services in this manner also supportsreconfiguration. In particular, when a node's configuration changes, forexample, because responsibility for some portion of the transactionspace is transitioned from one server to another, the changes arequickly and efficiently communicated via the name service's mappingsystem. Another advantage of using the CDN name services supports thenotion of suspension. Thus, in the event an edge element or core nodeelement becomes impaired or inoperative, the mapping system can maptraffic away from the problem. A further advantage of using the CDN nameservice is the ability of such systems to support load balancing oftraffic based on high resolution capacity consumption measurements. Thisapproach also supports route and region diversity, such that a device inthe periphery may receive addressing information for edge elements thatshare minimal underlying service and network components. CDN DNSservices also support latency optimization. For example, core nodeelements may receive addresses for other core node elements that meetsome proximity criteria.

An alternative embodiment utilizes location or direction-aware mapping.Thus, for example, a core node element may use domain names encoded withlocation or direction information (either geographic or topologicaldirection) such that responses provide addresses to node elements thatare in a desired location or direction or that comprise a directionalgraph. This capability may be intrinsic to the mapping system or anadjunct thereto. Topological mapping in this manner provides for a lowlatency, topology aware data propagation mechanism.

Generalizations

As used herein, a block generally refers to any aggregation orassociation of transaction data. There is no specific format required. Ablockchain is a continuously growing list of records, called blocks,that are linked and secured using cryptography. Each block in ablockchain typically contains a cryptographic hash linking to theprevious block, and transaction data. For use as a distributed ledger, ablockchain is typically managed by a peer-to-peer network collectivelyadhering to a protocol for inter-node communication and validating newblocks. Once recorded, the data in any given block cannot be alteredretroactively without the alteration of all subsequent blocks, whichrequires collusion of the network majority.

While the techniques herein may use a blockchain to record transactiondata, this is not a limitation, as the architecture and associatedtransport mechanism of this disclosure system is also applicable toother organizations of transaction data. Moreover, the notion of ablockchain, as in a chain or sequence of blocks, may be any organizationof blocks including, without limitation, a block tree, a block graph, orthe like.

Mining is the act of generating an ordered block of transactions with aheader that references a previous block in the blockchain. In public(permissionless) blockchain consensus systems, mining generally isstructured as a competition; if a generated block (and its ancestors)survive the mining competition and subsequent consensus process, it isconsidered finalized and part of the permanent record. In an idealsystem, mining responsibility from one round to the next (i.e., from oneblock to the next) is randomly-dispersed across participants. Formally,in an ideal system, mining decisions are not predictable, not capable ofbeing influenced, and are verifiable. In real world applications,however, the dispersion need not be perfectly random. For example, inproof-of-work systems, the dispersion is not actually random, asentities with more mining power have a higher probability of winning thecompetition.

Segmentation

Traditional blockchain implementations treat the blockchain as a simplesequence of blocks. Such approaches severely limit the achievableperformance of blockchain implementations, typically by creatingbottlenecks in processing, communicating and storing the blockchain inits aggregate form.

In contrast, the approach described here departs from known techniquesby organizing the data of a single chain in a manner that allows itscommunication, processing and storage to be performed concurrently, withlittle synchronization, at very high performance. Preferably, and aswill be seen, this data organization relies on segmenting thetransaction space within each node while maintaining a consistent andlogically complete view of the blockchain. This approach may also beapplied to each of multiple chains that comprise a set of federated orsharded blockchains, and to improve the performance of the blockchainoperation thereby reducing the work and increasing the performance ofoff-chain (so-called “Layer-2”) systems.

In this approach, the consensus algorithm that spans the network is usedto ensure the system produces correct finalized results. The particularconsensus algorithm(s) that may be used are not a limitation. Operationswithin each node, however, assume the elements of the node are correctand trustworthy. If a node fails or is corrupted by an adversary, thesystem relies on the rest of the network to maintain service integrityand availability as well as to support failure and intrusion detectionfunctions. As will be seen, this design architecture enables theinternals of a node to be organized as a loosely-coupled distributedsystem running on a high performance, low latency communications fabricsuch that system elements are aligned with the blockchain dataorganization. The resulting architecture provides a much higherperformance implementation as compared to known techniques.

Block Segmentation

Referring to FIG. 2, a block 200 is segmented by transaction id (Tx_(i))into some number of segments 202 a-n, where n=1000, and a header 204.The segments 202 and header 204 represent a block of the blockchainalthough they may be (and often are) processed, transmitted and storedseparately. The number of segments 202, shown in FIG. 2 as 1000, may bemore or fewer in number and may change over time or dynamically.Preferably, a sufficient number of segments is selected to create aspace that is large enough to enable substantial future growth of theunderlying resources without having to change the segmentation (theorganization) of the data.

In this embodiment, block segmentation typically is an externallyvisible attribute shared by all nodes of the network. As will be seen,organizing the block data by segment significantly improves theperformance and efficiency of nodes exchanging block information. Inparticular, the approach herein enables the components of a noderesponsible for handling a given segment to communicate directly withthe components of other nodes responsible for handling the givensegment. Moreover, the mapping of segments to components may differacross nodes, thereby allowing for scaled-up (or scaled-down)deployments, e.g., by allowing nodes to employ a different number ofresources in handling the overall amount of transaction data.

In an alternative embodiment, the details of the segmentation may remainstrictly a node internal attribute. In such an embodiment, the mappingof segments to the components of a node may be arbitrary. Thisalternative allows greater independence in the configuration of nodes,but it generally requires more granular (e.g.,transaction-by-transaction) exchange of data between nodes involvingsome form of transaction layer routing inside the nodes.

As used herein, the term segmentation is used to mean any grouping,partitioning, sharding, etc. of transaction data, whether implicit orexplicit, such that the elements of one node may interact with elementsin another node to exchange data for more than one transaction at atime.

A header 204 includes several required elements, namely, a hash 210 ofthe previous block header, a Merkle root 208 of the block's contents,and a proof 206 indicating that a miner of the block in fact was alegitimate miner. Other information may be included.

Blockchain Segmentation

Referring to FIG. 3, the segmented blocks form, temporally, a segmentedblockchain, with some blocks thereof pending (i.e., not yet finalized),while other blocks thereof are finalized (i.e., added to theblockchain). In this example, each machine 300 as depicted supports bothpending and finalized blocks, although this is not a requirement. Thisdistributed organization is not limited to a block “chain,” as theapproach may also be applicable in other scenarios, such as with respectto a block tree or block graph structure. The approach is advantageousbecause the blocks are still whole but the segments thereof areprocessed more efficiently than processing a block monolithically. Asdepicted in FIG. 3, a varying number of segments may be assigned todifferent machine resources and commingled. This type of organization isparticularly applicable to virtualized and containerized environments,although neither are required to achieve the benefits.

Referring to FIG. 4, the assignment of segments to system resources mayvary over time, for example, to support upgrades, maintenance andfailure recovery. In this case, one machine 402 failed or was taken offline, and the segments it was handling are then migrated to othermachines. This approach fits well with established concepts of migratingvirtual or containerized computing elements both for routine andemergent reasons.

Segmentation and Inter-Node Communication

Referring to FIG. 5, by making segmentation a publicized attribute of anode, elements within a node may communicate directly with elements inother nodes to exchange information on the granularity of a segment. Themapping of segments to nodes need not be the same across all nodes.

As will be described, in a preferred embodiment the computing nodes ofthe system are each capable of performing (and often do perform)multiple distinct functions or modes (operating roles) such astransaction validation, as well as block mining and verification.Indeed, a given computing node often operates in multiple such modes atthe same time. In a typical operating scenario, particular nodes may beused for mining, although typically all computing nodes verify what ismined.

FIG. 5 illustrates how orchestration of block mining and blockverification preferably is accomplished in the presence of segmentation.In this example, it is assumed that there are a number of machines thatare used for generating/mining the block in the computing node 500 a,while other computing nodes 500 b, 500 c and 500 d comprise machinesthat verify the block (referred to herein as “verification”). Asdepicted, a block mining event is initiated by message 502 sent by amining node 500 a (generally by the element that handles the generationand validation block headers) to the other nodes of the network (in thisexample, nodes 500 b, 500 c and 500 d) informing them that it is aboutto begin mining or generating a block. Corresponding elements in nodes500 b, 500 c and 500 d receive this message and inform their node'sprocessing elements to expect mined block data from elements in themining node. At the same time, multiple sequences of messages like 503are sent for each generated segment by the elements in the mining nodehandling those segments to the elements handling each segment in remoteverification nodes (respectively).

Once a mined segment is finished, message 504 is sent from the elementresponsible for that segment to the element responsible for the blockheader. The message includes, among other things, the Merkle root of thegenerated segment. Once all messages 504 are sent and received, theelement responsible for the block header creates the top of the blockMerkle tree and saves the Merkle root in the header. It then transmitsmessages 505 to the elements in the other nodes responsible for handlingheader generation and verification. In performing validation, and uponreceiving messages 503 for a segment, the receiving node elementhandling the segment validates the received transactions, computes thesegment's Merkle tree, and upon completion sends message 506 to theelement in the node handling the header. That element reconstructs theblock header from the messages 506 for all segments and compares it tothe header received from the mining node in message 505. If the headersmatch, the block is accepted and added to the set of pre-finalizedblocks in that node.

In one embodiment, if the transactions fail to verify or thereconstructed header does not match the header transmitted from themining node, the block is rejected, and all changes are reverted andexpunged from the node.

In another embodiment, validating nodes can flag machines that mine to adifferent value of message 506 for the same segment, therebysafeguarding the system from one or more faulty or malicious machines.

The above-described processing is described in more detail below.

Segmentation and Node Orchestration

FIG. 6A and FIG. 6B depict the operation of a computing node of thesystem, with FIG. 6A showing the operation of the node elements involvedwith initial transaction validation, and FIG. 6B showing the operationof the node elements involved with block mining and verification.

As depicted in FIGS. 6A and 6B, a node comprises several elements orcomponents that work together to perform separately scalable tasksassociated with transaction validation as well as block mining andverification. These components include node coordinator 601, a set ofsegment handlers 604, a set of transaction handlers 609, a set of UTXO(Unspent Transaction Output) handlers 614, and a set of signatureverifiers 617. While segment and transaction handlers are shown asdistinct (and this is preferred), these functions can be combined into acomposite handler that performs both functions as will be described.Further, while typically there are a plurality of instances of eachhandler, one may suffice depending on its processing capability.

By way of background, and as noted above, preferably each node isfunctionally-equivalent to all other nodes in the system, and each nodecarries the entire load of the system. More generally, all nodes in thesystem are considered to be equal to one another and no individual node,standing alone, is deemed trustworthy. Further, with respect to oneanother, the nodes operate autonomously, and no node can control anothernode.

A node operates in general as follows. For transaction validation, andwith reference to FIG. 6A, raw transactions are continuously received atthe node at 612, typically as those transactions are forwarded from theedge machines (or from other nodes), and initially processed by thetransaction handlers 609. A transaction typically is formulated in awallet or a set of wallets (e.g., by a wallet service associatedtherewith or running thereon), and the wallet typically interacts withan edge machine either to receive a transaction request from theperiphery or to forward a blockchain transaction to the core, where itis received at 612 and processed by a transaction handler 609. Ingeneral, the processing of a raw transaction by a transaction handler isa “validation,” and once a raw transaction is “validated” by thetransaction handler, the transaction is placed in the transactionhandler's memory pool (or “mem pool”). A raw transaction that is notfound by the transaction handler to be valid is rejected and not placedin the handler's mem pool.

To this end, upon receipt (i.e. ingress of a raw transaction to thenode), the transaction handler 609 typically carries out two basicactions. As depicted in FIG. 6A, the transaction handler 609 queriesUTXO handlers 614 (at 615) to determine whether inputs to thetransaction exist and, if so, to obtain those inputs (at 616) from theUTXO space being managed by the UTXO handlers 614. If the inputs do notexist, the UTXO handler that receives the query informs the transactionhandler, which then rejects the raw transaction. Upon receipt of inputsfrom the UTXO handler 614, the transaction handler 609 consults asignature verifier 617 (at 618) to determine whether a unlocking script(digital signature) associated with each input is valid. Typically, eachinput contains an unlocking script (digital signature) of thetransaction, and thus the signature verification performed by asignature verifier involves the signature verifier checking that thesignature matches the locking script (pubic key) associated with eachUTXO consumed by the transaction. Further details regarding thisoperation are described below. This check thus involves a cryptographicoperation and is computationally-intensive; thus, the signature verifierpreferably is only consulted by the transaction hander for a valid inputreceived from the UTXO handler. The signature verifier 617 acknowledgesthe validity of the input (in particular, the input signature) at 619.The transaction handler can interact with the UTXO handler and thesignature verifier concurrently as inputs are received by thetransaction handler. Once all input signatures are verified by thesignature verifier 617, the raw transaction is considered by thetransaction handler to the “valid” or “validated,” and at 615transaction handler 609 creates new transactions outputs (UTXOs) in theUTXO handler 614 responsible for UTXOs associated with the newtransaction. In this operation, a create request is sent to only oneUTXO handler, namely the one handler that handles UTXOs in the portionof the transaction id space associated with the transaction. As alsodepicted, the create call (at 615) is sent (after a query and signatureverifier success) to initiate the new transactions outputs (UTXOs).

Once all inputs are verified in this manner, the raw transaction is thenplaced in the transaction handler's mem pool. The raw transaction (thathas now been validated) is then output (i.e. propagated) to all othernodes via 613, and each other node that receives the raw transactioncarries out a similar set of operations as has been just described. Thiscompletes the local validate operation for the raw transaction, which asa consequence is now in the transaction handler's mem pool. Theabove-described process continues as raw transactions are received atthe node (once again, either from edge machines or from other nodes).

Thus, a transaction handler that receives a raw transaction determines(from querying the UTXO handler) whether inputs to the transactionexists and, if so, what are their values and locking scripts (containingpublic keys sometimes referred to as addresses or wallet addresses). Itchecks each input's unlocking script (digital signature), and if allsignatures are valid, the transaction handler commits (saves) the rawtransaction to its associated memory pool. In this manner, validated rawtransactions accumulate in each handler's mem pool. Thus, in eachtransaction handler's mem pool there are a collection of transactions ineffect “waiting” to be mined (i.e., assigned) to a block segment (andthus a block) in the blockchain. Preferably, the system enforces aminimum wait time to allow the new transactions to propagate and bevalidated by the other nodes of the system.

Assume now that the node coordinator 601 determines it is time to mine ablock into the blockchain. The notion of mining a block is distinct fromthe notion of actually adding the block to the blockchain, which happens(as will be described in more detail below) when the node coordinatordecides a block is final according to a prescribed consensus algorithmof the system. Typically, at any given time there is a subset of thenodes that act as “miners.” According to the techniques herein, and ashas been described, in lieu of mining a block as a composite, a block ismined in “segments,” i.e., individual segments of the block are minedseparately (albeit concurrently or in parallel) and, in particular, bythe segment handlers 604.

To this end, and with reference now to FIG. 6B, the node coordinator 601instructs its associated segment handlers 604 to begin mining theirsegments via 605. This command typically includes a start time, aduration, and an end time. The node coordinator also informs other nodecoordinators in the system (via 602) to expect mined block segment datato be transmitted directly (via 607) from the mining node's segmenthandlers to the segment handlers in the other nodes of the system. Asegment handler's job is to obtain and receive validated rawtransactions from a transaction handler's mem pool, and to stage thosevalidated transactions for eventual persistence in the block segment(and thus the block) if and when the block is finalized and added to theblockchain. In an alternative embodiment, the segment handler may obtainand receive digests (hashes) of validated transactions, in which casethe job of staging transactions for future persistence shifts to thetransaction handler.

As will be described, preferably the actual persistence of each segmentin the block (and the persistence of the block in the blockchain itself)does not occur until the segment handlers are instructed by the nodecoordinator to finalize a block. Typically, there is a 1:1 relationshipbetween a segment handler 604 and a transaction handler 609, althoughthis is not a limitation. As noted above, these functions may becombined in an implementation and while a 1:1 relationship is depicted,a node could be configured with any number of either type of handler.

Upon receipt of the command to initiate mining, at 610 the segmenthandler 604 requests the transaction handlers (handling segments for thesegment handler) to assign transactions in their respective mem pools tothe block and return each raw transaction (or a hash thereof). Beforethe transaction handler returns a raw transaction from its mem pool tothe requesting segment handler, however, the transaction handler mustfirst “spend” the transaction inputs with respect to the block beingmined (i.e., apply the actual transaction values to the inputs), whichit does by sending spend requests (via 620) to the UTXO handlers; asdepicted, the UTXO handlers apply the spend requests, update their localdata, and return the result (success or failure) to the transactionhandler (via 621).

In the event of a failure response, the transaction handler mustinstruct the UTXO handlers via 620 to undo all successful spendoperations for the transaction. This collision detection and rollbackconstitutes an optimistic concurrency control mechanism that obviates,and thus avoids the high costs of, acquiring a lock (or a distributedlock in the case of a node with multiple UTXO handlers) on the UTXOhandler(s). This enables efficient high throughput, low latency handlingof UTXO spend operations.

Upon successfully spending all the transaction inputs, the transactionhandler instructs a UTXO handler via 620 to assign the transactionoutputs (the transaction's UTXOs) to the block, and it forwards via 611the raw transaction (and/or a digest thereof) back to the requestingsegment handler.

The segment handler-transaction handler interactions here as justdescribed are carried on as the transaction handler(s) continue toreceive and process the raw transactions as depicted in FIG. 6A anddescribed above. Referring back to FIG. 6B, the segment handlers 604operate in parallel with respect to each other, with each segmenthandler making similar requests to its associated transaction handler.Thus, typically, there is a segment handler-transaction handler pairassociated with a particular segment of the block being mined. Thetransaction handler 609 responds by providing the requesting segmenthandler 604 with each raw transaction from its mem pool, together with adigest that has been computed for the raw transaction. The segmenthandler 604 receives each transaction (and its digest) and sequences thetransactions into a logical sequence for the segment. Each segmenthandler operates similarly for the raw transactions that it receivesfrom its associated transaction handler, and thus the segments for theblock are mined concurrently (by the segment handlers). As the segmenthandler sequences the raw transactions, it takes the digests of thetransactions and outputs them (preferably just the digests) to all ofthe other nodes (via 607). The other nodes of the network use thedigests propagated from the segment handler(s) to validate the segmentthat is being mined locally. A segment handler also receives digestsfrom other segment handlers (in other nodes) via 608.

Once a segment handler 604 determines that a segment is valid, itreturns the result of its processing, namely, the root of a Merkle treecomputed for the segment, to the node coordinator via 606. During miningthe node coordinator trusts that the segments are valid. The othersegment handlers 604 (operating concurrently) function similarly andreturn their mining results indicating that their segments likewisecomplete.

Once all of the segment handlers respond to the node coordinator (withthe Merkle roots of all segments), the node coordinator then computes anoverall block Merkle tree (from all the segment Merkle roots) andgenerates a block header incorporating the overall block Merkle root andother information. The node coordinator then transmits/propagates aMining Done message via 602 containing the block header to the othernode coordinators in the network, and those other node coordinators thenuse the block Merkle root to complete their block verification processas will be described next.

In particular, assume now that the node coordinator 601 receives aMining Start message via 603 transmitted from the node coordinator ofanother node initiating its own block mining operation. This begins ablock verification process for block data mined and transmitted from theother node. The block verification process is a variation on the blockmining process, but the two are distinct and frequently a node will beengaged in both processes simultaneously. Indeed, while a node typicallymines only one block at a time, it can be verifying multiple incomingblocks simultaneously. As with mining, according to the techniquesherein, and as has been described, in lieu of verifying a block as acomposite, preferably a block is verified in “segments,” i.e.,individual segments of the block are verified separately (albeitconcurrently or in parallel) and, in particular, by the segment handlers604.

To this end, via 605 the node coordinator 601 instructs its associatedsegment handlers 604 to receive transaction hashes at 608 from othernodes and, in response, to verify the associated transaction blockassignments made by the mining node's segment handlers as theymine/assign transactions to a block in the mining process. Preferably,verification of segment data is performed progressively (as the data isreceived) and concurrently with the mining/assignment of additionaltransactions to the block segments in the mining node.

Upon receipt of a transaction hash, via 608, a segment handler 604forwards the transaction hash via 610 to the transaction handler 609responsible for handling transactions for the segment. Upon receiving atransaction hash from a segment handler, the transaction handler 609looks up the associated transaction record in its mem pool.

In the event the transaction is missing from the mem pool, transactionhandler 609 sends a request (via 622) to receive the missing rawtransaction (via 623), preferably from the transaction handler in themining node responsible for having mined the transaction. Thisrequest/response action preferably is handled at high priority in anexpedited manner. Upon receiving the missing raw transaction, and priorto resuming verification of the transaction's block assignment, thetransaction handler 609 must validate the transaction as described abovebefore adding it to its mem pool.

Upon successfully retrieving the transaction from its mem pool, thetransaction handler performs an assignment of the transaction to theblock segment being verified just as it assigns transactions to blocksbeing locally mined as described above; if, however, the assignmentfails, verification of the segment and the block of which it is a partfails (i.e., the block is rejected).

Subsequently, the node coordinator, applying a prescribed consensusalgorithm, decides to finalize a block. To this end, the nodecoordinator persists the block header, and it instructs the node'ssegment handlers to finalize the block. In so doing, the nodecoordinator provides the overall block Merkle tree to each segmenthandler. Each segment handler, in turn, persists its set of segmentsassociated with the block, and it instructs its associated transactionhandlers to finalize the block. In so doing, the segment handlersgenerate and provide to the transaction handlers the portion of theblock's overall Merkle tree each transaction handler needs for its setof segments. Each transaction handler, in turn, removes the finalizedtransactions from its active mem pool, and it responds to anyoutstanding transaction requests it received from the edge (or wallet)for finalized transactions and, in particular, with a Merkle proofderived from the portion of the block's overall Merkle tree thetransaction handler received from the segment handlers. The transactionhandler then saves the finalized transaction in memory, where it may beused to support subsequent queries that the transaction handler mayreceive concerning the disposition of a transaction. The transactionhandlers then instruct all UTXO handlers to finalize the block. Inresponse, the UTXO handlers mark UTXOs spent in the finalized block aspermanently spent, and mark UTXOs assigned to the finalized block aspermanently created. Persisting the block header and segments to disk inthis manner thus adds the block to the blockchain. Depending onimplementation, the block so written to the blockchain may then beconsidered final (and thus in effect immutable).

Summarizing, in the node processing described above, transactionhandlers receive raw transactions, typically from the edge machines.After a transaction handler validates the raw transaction (and places itin its local mem pool), the transaction handler propagates the rawtransaction to the appropriate transaction handlers in other nodes thatare also responsible for validating that raw transaction. Subsequently,and in response to a determination by the node coordinator to beginmining a block segment, the transaction handler mines (assigns) a set ofraw transactions from its mem pool to the block segment, and sends thoseraw transactions (and their associated digests) to the requestingsegment handler that is handling the respective segment. The segmenthandler sequences the received transactions into the segment and, as itdoes so, the segment handler forwards the list of digests for thetransactions comprising the segment to the other segment handlersresponsible for handling those segments in the other miner nodes. Thus,raw transactions propagate across the transaction handlers in all nodes,but segment handlers preferably only send the transaction digests forthe segments to be verified. During block segment mining andverification, transaction handers consult their local segmenthandler(s), which as noted communicate with the segment handlers ofother nodes. Transaction handlers in different nodes thus communicatewith one another to populate their respective mem pools withtransactions that have been validated (using the UTXO andsignature-verifiers). The segment handlers (and thus the nodecoordinator handling the mining) communicate with one another topopulate the blockchain with a block comprising the segments. Aspreviously noted, the transaction handlers and segment handlers need notbe separate services.

As described above, block verification is similar to block mining,except that for verification the segment handler is feeding transactionhashes to its transactions handlers, which transaction handlers thenrespond with “valid” (with respect to the raw transaction) or “invalid”(with respect to the entire received block), and the latter responseshould not happen unless the miner is behaving erroneously or in anadversarial manner. The above-described technique of generating andhandling of Merkle trees and roots is the preferred cryptographicmechanism that ties transactions to their block. In verification, andupon completion when the node coordinator gets results from all thesegment handlers, the coordinator once again computes the overall blockMerkle root, but this time it compares that root with the root providedin the block header sent to it by the mining block coordinator. If theydo not match, the block is discarded as invalid.

The terminology used herein is not intended to be limiting. As usedherein, the term “validate” is used for the operation that thetransaction handler does when it receives a raw transaction to be put inits mem pool. As noted above, to validate a transaction, the transactionhandler queries the UTXO handler(s) to check the availability of thereferenced UTXOs and talks to the signature-verifier to check signatures(on the inputs). In contrast, the term “verify” is used for the act ofverifying the contents of block segments received from other nodes thatare likewise performing the consensus initiated by the node coordinator.A transaction validation may also be deemed an “initial transactionverification” as contrasted with the “block segment verification” (whatthe coordinator and segment handlers do with block segment data receivedfrom other nodes) in response to the coordinator initiating a miningoperation on the block (comprising the block segments). Also, the term“mine” is sometimes referred to as “assign,” meaning what a transactionhandler does when it is told by the segment handler to assign orassociate a transaction with a block segment, i.e., the transactionhandler's verification of the transaction with respect to its inclusionin a block segment by the segment handler. As noted above, to accomplishthis, the transaction handler communicates with its UTXO handler to“spend” existing UTXOs, and to “assign” new UTXOs to a block segment.

Also, the notion of a “handler” is not intended to be limited. A handleris sometimes referred to herein as a “coordinator,” and the basicoperations or functions of a handler may be implemented as a process, aprogram, an instance, an execution thread, a set of programinstructions, or otherwise.

While the above describes a preferred operation, there is no requirementthat a handler handle its tasks on a singular basis. Thus, a segmenthandler can handle some or all of the segments comprising a block. Atransaction handler can handle the transactions belonging to aparticular, or to more than one (or even all) segments. A UTXO handlermay handle some or all partitions in the UTXO space. The term“partition” here is used for convenience to distinguish from a segment,but neither term should be deemed limiting.

The following provides additional details regarding the above-describednode components in a preferred implementation.

Node Coordination

Node coordinator 601 participates in a network consensus algorithm todecide whether the node should mine a block or not, and from what othernodes it should expect to receive mined block data. If the node is tomine a block, node coordinator 601 sends messages (via 602) to the othernode coordinators in the network. Node coordinator 601 also receivesmessages (via 603) from other node coordinators in nodes that are mininga block. As has been described, node coordinator 601 informs the node'ssegment handler 604 in messages (via 605) to start mining block segmentsand from what other nodes to receive and validate mined block segments.The node's segment handler 604 will return to the node coordinator 601in a message (via 606) the Merkle root of the transactions comprisingeach block segment.

Another aspect of node coordination is managing node localrepresentations corresponding to the one or more chain branches that maybe active in the network at any given time. Typically, a blockchainconsists of a single sequence of blocks up to the point of finalization.Finalization often is set to be some number of blocks deep in the chain,but the decision of what and when to finalize is subject to the rulesgoverning consensus across the network. The part of the blockchain thatis pre-finalized consists of potentially multiple branch chains that getresolved before finalization. As indicated above, for example, whenmultiple nodes mine simultaneously, they fork the blockchain intomultiple branches that have some common ancestor block. The nodecoordinator 601 is responsible for tracking active branches andinforming the segment handlers 604 which branch they are mining, if thenode is mining, and which branch each remote miner is mining.

Segment Handling

As also described, segment handlers 604 handle the generation and/orvalidation of some number of block segments representing a portion ofblock segmentation space. Specifically, the segment handlers begingenerating block segments as directed by the node coordinator 601 inmessages (via 605). When mining, a segment handler 604 transmits minedblock segment data via 607 to segment handlers in the other nodes to beverified. A segment handler 604 receives block segment data in messages(via 608) from segment handlers in mining nodes. To perform transactionmining and validation, a segment handler 604 interacts with anassociated set of transaction handlers 609 as also previously described.

Transaction Handling

Transaction handlers 609 handle the validation of transactions to beadded to the mem pool and propagated to the network, the generation oftransactions to be included in a mined block, and the verification oftransactions to be included as part of a block received from a miningnode. As noted above, the distribution of the transaction segmentationspace may be the same for a transaction handler 609 and a segmenthandler 604, or it may be different. For example, the computationalresources needed by the segment handler function may be sufficiently lowthat only a few such handlers are used to handle all the block segments,whereas the computational resources required by the transaction handlerfunction might be sufficiently high so as to require that each suchhandler manage the transactions for a smaller number of segments thantheir associated segment handler 604.

The transaction handler function plays another important role in thesystem as also previously described, namely, transaction admissions(also referred to as “validation”) and propagation. A transactionhandler 609 receives transactions in messages (via 612) from the edgeeither directly or indirectly via other transaction handlers in thenetwork. The transaction handler 609 validates all received transactionsand if valid, saves the transactions to a pool of unprocessedtransactions (its mem pool) and optionally propagates the transactionsto other nodes in the network in messages (via 613). In this way, thetransaction handler function orchestrates the propagation of transactiondata such that all nodes receive all incoming transactions andassociated incoming transaction digests in a timely and efficientmanner.

UTXO Handling

Preferably, UTXOs are identified by an identifier (txid), which is ahash or digest of the originating transaction, and the index of theoutput in the originating transaction. A UTXO also has two other piecesof information (not used in its identification), namely, a value, and a“locking script.” Generally, the locking script is a set of instructionsor simply a public key associated with the output. Sometimes the publickey is called an address or wallet address. The locking script (e.g.,the public key) is conveyed in the output of a transaction along withthe value, and typically it is stored in a UTXO database along with theUTXO identifying information and its value. Thus, a query to the UTXOhandler during initial transaction validation returns both the value andthe locking script (public key). To spend a UTXO as an input to a newtransaction, the new transaction (essentially its outputs), must besigned by the private key cryptographically matching the public key ofthe UTXO to be spent. This signature is provided with each transactioninput and is generally called the “unlocking script.” The unlockingscript can be a set of instructions or simply a digital signature. Thus,the digital signatures bind the output values of the transaction to thelocking scripts (public keys) for which the receivers of the valuespresumably have the corresponding private key (later used to formulatean unlocking script). The signature verifier does not have the privatekey (as only the wallet or cryptographic element thereof has the privatekey). The signature verifier receives the public key (from the lockingscript) and a signature (from the unlocking script), and the signatureverifier verifies the signature against the public key, thereby provingthe signature was produced by the matching private key. To summarize, atransaction output at a given index has a locking script (public key)and value. A transaction input has the originating txid, index, and anunlocking script (signature).

To handle transactions, and as noted above, the transaction handlerinteracts with a set of UTXO handlers 614 with messages (via 615 and620) to create, query, spend, and assign Unspent Transaction Outputs(UTXOs) associated with each transaction. Each UTXO operation may alsobe reversed using an undo request in messages (via 620). Thisreversibility is valuable because it allows for a transaction handler609 to undo the parts of transactions that may have completedsuccessfully when the transaction as a whole fails to complete. Insteadof locking UTXO databases to allow concurrency and prevent conflicts,here the system preferably relies on detecting conflicts and reversingUTXO operations for partially complete transactions. Conflicts in thiscontext include, but are not limited to, an attempt to spend a UTXObefore it exists or is finalized (as policy may dictate), spending aUTXO that has already been spent by another transaction, or any otherUTXO operation failure that renders the transaction incomplete.

As noted above, each UTXO has a value and an locking script that must beexecuted successfully for the transaction to validate. The script is aset of instructions that must be executed to lock the use of a UTXO asan input to another transaction. Commonly, the script contains publickey material that corresponds to the private key that must be used tosign transactions that consume the UTXO as an input.

Because the number of UTXOs that accumulate can grow large, the UTXOspace preferably is also partitioned by transaction identifier in amanner similar to how blocks are segmented by transaction identifier,although preferably the partitioning and segmentation spaces are dividedaccording the needs of each independently. While UTXO handling could beperformed by the transaction handlers that produce the UTXOs, preferablythe handling of UTXOs is separated out from transaction handling for tworeasons: (1) because the resource demands are different, and (2) becauseisolating the transaction handler function enables the transaction andUTXO handlers to perform more efficiently. Preferably, the UTXO spacealso is partitioned to make more efficient use of a node's aggregatememory and storage resources. By applying this segmentation (namely,through the transaction segmentation space), a highly scalable andtiming-constrained solution is provided.

Signature Verification

The final element in the block diagram in FIG. 6A is the signatureverifier function provided by a set of signature verifiers 617. As notedabove, preferably transactions are signed by the set of private keysassociated with the transaction's inputs. The most compute intensivetask in a node is verifying the signatures of a transaction.Consequently, significant computational resources preferably arededicated to signature verification. Each signature verifier 617preferably harnesses the computational resources necessary to support aportion of the signature verification load, and the transaction handlerfunction disperses the signature verification load across the availableset of signature verifiers 617 using messages (via 618) to send the datato be validated, and in return receiving acknowledgement or negativeacknowledgement in messages (via 619). In one embodiment, theseoperations are carried out by combining signature verification with someother processing (e.g., transaction handling). In another embodiment,and as depicted and described, to allow for greater scalability, theprocessing demand is accommodated by enabling signature verifiers 617separate from other elements.

Pipelined Block Generation, Transmission, and Verification

Referring to FIG. 7, traditional blockchain based systems serialize thegeneration (mining), transmission, and verification of blocks. In suchsystems, a block is generated 701 by a miner; once the block is finishedbeing generated, it is transmitted 702 to other nodes for verification,and once nodes finish receiving a block, they begin to verify 703 theblock. Such serial-based processing is inefficient and does not scale,especially in the operating context previously described, namely,wherein transaction messages are being generated across a potentiallyglobal-based network.

When attempting to build a system with high performance requirements,e.g., such as being capable of processing millions of real-timetransactions per second, such current implementation approaches areentirely inadequate. For this reason, in the approach herein (and asdescribed above), preferably these processing stages are pipelined forconcurrency. Thus, according to the techniques herein, while a minergenerates 704 block data, previously-generated block data is transmitted705 to nodes for verification. The verifying nodes receive the minedblock data and begin verifying 706 the block's transactions beforereceiving the complete block and likely long before the miner hasfinished mining the block.

It should be appreciated that in accordance with FIG. 5, the pipeline ofblock generation, transmission and verification also is instantiated foreach segment of a block and that, as such, block segments are operatedon in parallel. The result is greater concurrency through thecombination of parallel and pipeline processing.

Streaming Block Generation, Transmission, and Validation

Referring to FIG. 8, to support pipelined block generation, transmissionand verification a streamed block segment generation, transmission andverification process is shown between two nodes, namely: miner node 801and verifying node 805. Although one verifying node 805 is shown, asdescribed above typically all nodes in the network verify the minedblock. As has also been described, this process also typically runsconcurrently with the same process for other block segments being minedby miner node 801. As noted, there may be multiple miner nodes 801 andmultiple streamed generation, transmission and validation processesoperating in the network concurrently. Note that in this example, theresponsibility of staging a segment for persistence is associated withthe transaction handlers as opposed to the segment handlers, asdescribed previously.

Generation

As shown in FIG. 8, the process starts when mining node coordinator 802meets the criteria for mining a block on the network. In one embodiment,this criterion could be a probability condition that the miner can proveit meets (e.g., a trusted or otherwise verifiable random number belowsome threshold). Any criteria for miner selection (leader election) maybe applied. Node coordinator 802 sends messages 809 to request thatmining node segment handler 803 start generating block segments. Nodecoordinator 802 also sends messages 810 indicating to the validatingnode's coordinator 806 to expect mined block segments from the minernode's segment handler 803. Each mining segment handler 803 sendsmessage 811 to their associated transaction handler(s) 804 indicatingthat transaction handler(s) 804 start assigning transactions from a poolof collected raw transactions associated with each transaction handler804 to a block. Transaction handler 804 repeatedly inspects unprocessedtransactions (transactions that have not previously been assigned to theblock or any ancestor thereof.) that it received from the edge (directlyor via transaction handlers in other nodes). It should be appreciatedthat some aspects of transaction verification (transaction validation asdescribed above) may be done in advance when the transaction is firstreceived. For each verified transaction assignment, transaction handler804 (1) adds the full transaction record 813 to block segment 831, and(2) sends message 814 containing a digest (e.g., a hash) in a stream tosegment handler(s) 803.

Transmission

Segment handler 803 collects one or more transaction digests from thestream of messages 814 and sends the transaction digests in a stream ofmessages 815 to the segment handler 807 in each validating node 805responsible for validating the generated segment data. As shown, thenumber of messages in the stream of messages 814 may differ from thenumber of messages in the stream of messages 815, though the totalnumber of transaction digests transmitted in both streams typically willbe the same.

In validating node 805, segment handler 807 receives a stream ofmessages 815, extracts the transaction digests, and sends one or moremessages 816 to transaction handler 808. The number of messagescomprising the streams of messages 815 and 816 may differ. In thisembodiment, transmitted message 810, stream of messages 815 ending withmessage 833, and message 823, may be transmitted unicast or multicast,directly from node element to node element, indirectly propagatedthrough elements in other nodes, or routed or forwarded through networkelements. The data may travel aggregated or separated.

Verification

Verifying transaction handler 808 receives the transaction digests andlookups unprocessed transactions it has received from the edge (directlyof via transaction coordinator in other nodes). If the lookup issuccessful, it verifies the transaction assignment. Upon successfulverification, transaction handler 808 (1) sends verificationacknowledgements in messages 818 to segment handler 807, and (2) addsthe full transaction record 817 to block segment 832.

End of Stream Handling

In one embodiment, the streaming generation, transmission, andverification process ends when mining node coordinator 802 sends a stopgeneration message 819 to all mining segment handlers 803. In thisscenario, nodes are assumed to be running asynchronously, and with noexplicit time boundary between execution rounds. In another embodiment,nodes may run in a synchronous manner, and the process would end when aspecific time is reached. When the process ends, each segment handler803 sends a stop generation message 820 to its associated transactionhandler 804. Each transaction handler 804 finishes or aborts anytransaction assignments that are still in progress and acknowledges thatit has stopped mining along with any remaining assigned transactionsincluded in the block segment in message 821 to segment handler 803.

Segment handler 803 sends any unsent transaction hashes and anend-of-stream indication in message 833 to validating node's segmenthandler 807. Each segment handler 803 computes a Merkle tree from thetransaction hashes of each segment and sends the Merkle tree root(Merkle root or MR) to the node coordinator 802 in message 822. When thenode coordinator 802 receives a Merkle root for all segments of theblock, it computes the top of the Merkle tree for the overall block fromthe segment Merkle roots and generates a block header composed a hash ofthe previous block header, its mining proof, and the overall blockMerkle root, and other data. On failure, node coordinator 802 send purgemessage 827 to each segment handler 803 which in turn sends a purgemessage 828 to its associated transaction handler(s) 804 that thendiscards the block segment. On success, node coordinator 802 sends theblock header in messages 823 to all validating node coordinators 806.

When each verifying node's segment handlers 807 receives end-of-streamindications in messages 833, they in turn send to their associatedtransaction handlers 808 messages 834 indicating the end-of-streamverification. When each segment handler 807 has receivedacknowledgements for all outstanding transaction assignmentverifications from its associated transaction coordinator 808, itcomputes the Merkle trees for its segments and sends the Merkle root foreach segment in messages 824 to verifying node coordinator 806. Whenverifying node coordinator receives Merkle roots for each segment, itgenerates a block header, and verifies that the block header itgenerates matches the block header it received in message 823. If theblock header does not match, it sends purge message 825 to eachvalidating segment handler 807 which, in turn, sends purge message 826to its associated transaction handler(s) 808 that then discards theblock segment.

Finalizing a Block

As noted above, in the above-described system a block is not persisteduntil it is finalized. Preferably, the block is not finalized until thenode coordinator concludes that is should be finalized based on havingadhered to a prescribed consensus algorithm. In contrast, preferably atthe conclusion of mining, a block is not persisted. Rather, aftermining, a block is simply tracked until it is either finalized (per theconsensus algorithm) or thrown away (purged), in the latter case becauseit did not survive the application of the consensus algorithm.

The techniques of this disclosure provides significant advantages. Inparticular, the approach leverages a high-quality, low-latency,highly-interconnected core network (the mesh) in conjunction with blocksegmentation and other above-described features (e.g., topology-awaredata propagation, non-blocking architecture, optimistic concurrencycontrol, partitioning, multicast and the other features) to provide acomputationally-efficient transaction processing system, all without anycentral transaction routing or switching (e.g., a Layer 7 switch thatneeds to account for an route large numbers of transactions).Preferably, the architecture is used in conjunction with a global CDNnetwork to provide global reach, and this approach advantageouslyenables CDN mapping technologies to be conveniently leveraged (e.g., byclients and other transaction services) to discover and interact withthe computing elements in the core network.

Concurrent Transaction Processing

The above-described design of a high performance distributed system ofrecord introduces the concepts of segmenting blocks, and partitioningthe Unspent Transaction Output (UTXO) data structures. As has beendescribed, the resulting data organization promotes increased concurrentprocessing with decreased synchronization, thereby resulting in a systemwith higher transaction throughput and lower transaction processingtimes.

The following section describes how to achieve safe and performanttransaction processing given the concurrent processing structure. Inparticular, the system needs to be resilient to erroneous or adversarialacts that attempt, for example, to spend UTXOs more than once. Thiscould happen, for example, if two instances of a wallet attempt to spendthe UTXOs currently associated with the wallet at the same time. Thiscould be intentional or unintentional. As will be seen, the followingdesign also addresses the cases of failed components, preferably byrelying on a broader network of nodes. As will be seen, the techniquesherein facilitate making concurrent processing safe in one or moreoperating scenarios, namely: (a) when the underlying components areoperating properly, (b) when there is redundancy in the underlyingcomponents such that broken components appear to be operating properly,and/or (c) when there is redundancy in the underlying components, withsuch redundancy being explicitly managed by the affected system elementsinvolved (i.e., transaction handlers and UTXO handlers).

Referring to FIG. 11, and with above-described distributed architectureas background, there is shown a general configuration with some number(N) transaction handlers 1101 communicating with some number (K) UTXOhandlers 1102 via communications networks composed of network elementssuch as switches 1103. As described in detail above, transactionhandlers 1101 process transactions for a set of segments in a segmentedtransaction space, and UTXO handlers 1102 process Unspent TransactionOutputs (UTXOs) associated with transactions in a partitioned UTXOspace. Segmentation and partitioning in this context mean similarthings, namely, dividing a space such that portions of the space may behandled separately. For convenience, these different terms are used toemphasize that these spaces can be setup in an independent manner(although this is not a requirement, as will be described below). Asdepicted in FIG. 11, for example, transaction handler 1101 is validatingtransaction 1105, which consists of input UTXO 1106, and outputs UTXO107 and UTXO 1108. In this example, which is merely representative, UTXO1106 is then handled by UTXO Handler 1102, while UTXO 1107 and UTXO 1108are handled by a different UTXO handler 1104.

Generalization

As noted above, typically the transaction segmentation and UTXOpartitioning spaces are distinct. In an alternative embodiment, thetransaction segmentation space and the UTXO partitioning space could bethe same, in which case typically UTXO handling then is combined(folded) into transaction handling. For example, in this approach aparticular transaction handler would in general communicate with othertransaction handlers to spend UTXOs associated with portions of thetransaction segmentation space that the particular transaction handlerdoes not handle.

Referring to FIG. 12, an example transaction hander and UTXO handlerdialog is depicted with respect to the use case in FIG. 11. Inparticular, and as depicted, the transaction handler 1201 communicateswith UTXO handler 1202 and UTXO handler 1203. In this example, thetransaction handler 1201 requests (at 1204) that UTXO Handler 1202 spendUTXO₀ and requests (at 1205 and 1206) that UTXO handler 1203 createUTXO₁ and UTXO₂. Upon completion, UTXO handler 1202 returns (at 1207) aspent message. Likewise, the UXX handler 1203 returns (at 1208 and 1209)the created UTXOs. It should be appreciated that, as an optimization,requests 1205 and 1206, as well as responses 1208 and 1209, could beaggregated into a single message each way. Transaction handler 1201knows which UTXO handler to use in each case based on what UTXOpartitioning scheme is used. For example, a UTXO may be mapped to a UTXOpartition based on a portion of the UTXO Transaction ID (the hash of thetransaction that created the UTXO), and the UTXO partition may be mappedto a UTXO handler based on metadata driving the system.

Spending one UTXO and creating two as a result is a common case (e.g.,pay a bill with one and collect the change in another), but there are nohard limits on the number of inputs and outputs in the concurrenttransaction processing design herein, and it is envisioned that therewill be cases where transactions have many inputs producing one output,one input creating many outputs, and many-to-many mappings as well.

Referring again back to FIG. 12, the inputs and outputs of a transactionmay be processed either sequentially or concurrently. FIG. 12 shows thembeing processed concurrently, and in general, there will be sometransactions with too many inputs or outputs to be processedsequentially within the time allotted for block generation andverification.

Collision Detection and Transaction Reversals

The use of multiple UTXO handlers to facilitate concurrent processing asdescribed above is not a requirement; indeed, there may be certaincircumstances, e.g., when one or more parts of a transaction fail whileone or more other parts succeed, or when two or more transactionhandlers collide over the use of one more UTXOs, where this approach isnot necessarily optimal. The following section addresses these issues,with FIG. 13 depicting the transaction failure-in-part scenario, andFIG. 14 depicting the transaction handler collision scenario.

FIG. 13 depicts an example failure case dialog between the transactionhandler and the UTXO handlers in the scenario of FIG. 12. Here, there isa transaction handler 1301, and two UTXO handlers 1302 and 1303. Thedialog in the failure case starts as it does in FIG. 12 (with steps1304, 1305 and 1306), but in this case (unlike in FIG. 12) one or morerequests failed. In particular, the request 1304 to spend UTXO₀ failedand the reason was returned in the response 1307; e.g., either the UTXOwas not found or is known to have been spent already. Also, the request1306 to create UTXO₂ failed for some system internal reason (resourceexhaustion or a failure to respond in a timely fashion) and response1309 indicates that failure. Note, however, that the request 1305 tocreate UTXO₁ returned normal response 1308 indicating the UTXO wassuccessfully created. The result of this dialog is an invalid state forthe affected handlers because the transaction partially succeeded; inother words, a UTXO got created even though the transaction failed.

As noted above, FIG. 14 depicts another failure case scenario, one inwhich a first transaction handler 1401 attempts to spend UTXO₀ inrequest 1405 and UTXO₁ in request 1407, while approximately at the sametime a second transaction handler 1402 attempts to spend the same UTXO₁in request 1406 and UTXO₀ in request 1408. The result of such concurrentaction could be a partial success of one or both associatedtransactions. As in the prior example, the partial success(es) renderthe state of the affected handlers invalid. This is a classic racecondition failure.

In traditional transaction databases, execution locks (mutual exclusion)would be used in both of the above failure scenarios to ensure thatvarious component operations either all succeed or all fail. Typically,this mutual exclusion is expressed as a transaction primitive so it canbe performed by the database server. A problem with this traditionalapproach, however, is that this locking is prohibitively expensive andyields highly variable response times, especially in the case where theoperations are distributed. Even a non-SQL database that supports objectversioning fails to address the failure cases. In particular, while thelatter approach protects an object from being updated if it does nothave its expected value, it does not protect against race conditionsspanning multiple such objects.

To address this problem, the concurrent processing design herein takesadvantage of an inherent property of UTXOs, namely they either exist orthey do not exist. (If a UTXO existed but has been spent, then bydefinition it does not exist anymore). To this end, preferably thedesign calls for each operation to be tagged with a transactionhandler-provided handle such that, if and when necessary, the operationmay be undone. It is then up to the transaction handlers collectively touse handles that are unique over some period of time. The period of timeis configurable, preferably based on the performance parameters of thesystem. As another aspect, preferably one or more policies are appliedthat prohibit the spending of UTXOs that are created in the same blockor even before they are finalized.

The UXTO handlers are located in the various computing nodes. Within acomputing node, UXTO data is stored in memory or other data storage inassociation with a UXTO handler. Thus, and as has been described, thetechnique of this disclosure provides for a lock-free distributed UTXOdatabase.

Referring to FIG. 15, this operation is now described using the samescenario as shown in FIG. 14. In this embodiment, and in contrast toFIG. 14, here there are transaction handler-provided handles given toeach operation. Thus, when the first transaction handler 1501 attemptsto spend UTXO₀ in request 1505 and UTXO₁ in request 1507, it associatesrespective transaction handler-provided handles, e.g., 11, 12, asdepicted. Likewise, when the second transaction hander 1502 attempts tospend UTXO₀ in request 1506 and UTXO₁ in request 1508, it associatesrespective transaction handler-provided handles, e.g., 21, 22. When partof a transaction then fails, the transaction handlers use the associatedhandle to undo all operations that may have otherwise succeeded. In thisexample scenario, after first transaction handler 1501 receives response1510 indicating the failure to spend UTXO₁, it issues Undo request 1512with handler h=11 to undo the operation of request 1505 that otherwisemay have succeeded. Likewise, the second transaction handler 1502 issuesUndo request 1515 with h=21 to undo the effects of request 1506. Notethat the Undo request is idempotent.

Although not shown, a similar mechanism may be constructed using handlesreturned by the UTXO handler (i.e., server-side handles). This latterapproach works so long as it is acceptable for a request timeout (inwhich case no server-side handle is available) to invalidate the stateof the handlers. With transaction handler-provided handles (i.e.,client-side handles), the effects of even timed out requests can beundone.

In the case of a transient network delay, the above-described mechanismthus protects from having to reconstruct the state of the affectedhandlers.

Accordingly, the general strategy as has been described is to detectcollisions in the use of UTXOs, and to safely reverse (back out or backoff) the affected transactions. In some cases, the errors may requirethe transactions to be denied but, in other cases, transactions may beretried again at a future time. An example of the latter is if a walletspends a UTXO before it is available.

The collision detection and undo mechanism as described above providesfor optimistic concurrency control in achieving consistency across thepartitioned and concurrently-processed UTXO data. Also, as describedabove preferably the system implements a policy that allows for thespending of a UTXO only after it has been mined into a previous block.As a consequence of this approach, there is no need to order andsynchronize the processing of a block segment (although the orderremains important with respect to creating the Merkle tree).

Use Cases

The above describes a high performance core distributed ledger andtransaction fabric for use, for example (but without limitation), in apayment network. Transactions are not limited to the primitive of movingvalue of sources to destinations, but rather any processing involvingthe transformation, conversion or transfer of value or information. Theperformance core provides the foundation to support a myriad of usecases including, without limitation, high performance transactionprocessing to financial systems.

As used herein, processing time is defined as the time elapsed betweenwhen an operation request (e.g., a financial operation request) isreceived and when a response is available. A particular operation mayrequire more than one transaction on the ledger. An operation isconsidered to be fully process when all required transactions have beensecurely stored in the ledger and all relevant business logic has beenexecuted. Preferably, processing time is on the order a couple seconds,if not less (e.g., sub-second). In addition to maintaining processingtime in this manner, the core network supports a high volume ofoperations. Operational throughput is defined as the rate at whichoperations are processed by the core network. A desired throughput maybe up to 10⁶ (or higher) operations per second, although this is not alimitation.

In one embodiment, the above-described architecture provides adistributed ledger, namely, a financial message ledger. The ledgerprovides an immortal log of transactions, secured with blockchaintechnologies as described. When used in this context, the networkincludes the ability to interface with existing financial transactionsystems, forwarding requests to and response from an acquirer (ACQ)and/or issuer (ISS). An alternative use case is a managed-value ledger,which enables the processing of transactions against a managed line ofcredit (or debit). This use case enables an ACQ/ISS to provision anon-network account balance that is subsequently credited/debited againstwithout contact with the ACQ/ISS. Transactions that exceed the managedcredit line can trigger a fallback to querying the ACQ/ISS to requestapproval. In a typical use, the transaction flow is as follows. Amessage is assumed to be approximately 1 KB in size. That message isreceived by the edge and distributed (from there) across the coreblockchain network. After the transaction is finalized (and a blockchainreceipt is received), a response is sent from the edge. In total, themaximum round trip time is preferably on the order of no more than two(2) seconds. In addition, the payment network is able to handle anend-of-day batch clearing process where an additional 1 KB message forevery processed transaction is sent of the payment network for clearing.These batched transactions is expected to be processed and logged withina few hours.

Any other use case requiring processing of transactions at a high rateand with low latency may benefit from this architecture. The managementof loyalty points is one non-limiting example of a non-monetaryapplication.

The architecture herein is also highly secure. Encryption,authentication, digital signatures and other technologies are used toguarantee customer privacy and data integrity.

The techniques herein provide for a global system of record thatexhibits high performance (in terms of number of transactions processed)and very low latency, all without sacrificing data security.

The managed network herein is a highly secure permissioned network.Accordingly, transaction collection and block construction times arereduced to near the time it takes to propagate a block across thenetwork. The approach herein takes advantage of the fact that networklatencies are generally sub-second between arbitrarily remote locationson the Internet; further, these latencies are further reduced by usingthe highly dispersed edge periphery and a less dispersed core in themanner that has been described.

The architecture described is highly-performant and overcomes the manyproblems that exist in known blockchain network environments, namely,network latencies, network utilization, confirmation depth, clock skew,topological bottlenecks and other factors. To facilitate the solution,as noted above preferably the core network itself has good geographicand topologic proximity. This is desirable, as consensus protocols (suchas are used in a blockchain network) often rely on large volumemessaging. Preferably, depending on the consensus protocol used, thecore network is to have low network latency and high interconnectivity,as this ensures that block propagation times remain timely with respectto the system's response time requirements. The overlay's secure edgenetwork is leveraged to ensure a fully global payment network that isstill highly-secure and high performance.

Blockchain systems include the concept of confirmations. Once atransaction is confirmed and added to a block in the blockchain, it isconsidered to have one confirmation. Each subsequent block added to theblockchain increase the level of confirmation of that transaction. Themore confirmations a transaction has, the more difficult it is for thetransaction to be removed from the blockchain. Most blockchain systemsadopt a convention of waiting a certain number of confirmations until atransaction is considered finalized and durable; this is referred to asthe “confirmation depth.” Preferably, the solution herein utilizes aconfigurable or variable confirmation depth to support transactionresiliency requirements.

Computing nodes in the core are time-synchronized, preferably using atime server.

The core network may be configured as a non-blocking full meshinterconnect topology. One preferred approach implements the corenetwork as a highly resilient partial mesh interconnect topology. Tobalance resilience (to network outages and attacks) versus blockpropagation times, however, preferably an efficient topology-aware datapropagation protocol is implemented, as has been described. The protocolis preferably built upon a multicast protocol where orchestration isdone in the network layer.

As used herein, a node is a high (upper) level unit of computing on thenetwork. Typically, a node comprises one or more physical machines(servers) that handle the node's workload. Preferably, theimplementation of a node is abstracted away from other nodes; to suchother nodes each peer node appears as a single entity on the network. Tosupport the transaction rate (e.g., one (1) million transactions persecond), preferably the node is configured into multiple physicalmachines. As noted above, preferably a node also has a time server thatis used to produce timestamps accurate to less than a millisecond. Inaddition, a node includes a cryptographic engine and random numbergenerator (RNG) server that is used to produce signatures and entropyneeded for consensus. Finally, the node includes transaction processingservers that are responsible for processing incoming transactions andappending them onto the blockchain in the manner described above.

In the permission-based approach as has been described herein, a nodeproves itself as a miner by providing a mining proof. A mining proof isdata presented by a node that mathematically proves the node is alegitimate miner of a block (or segment thereof). The proof is recordedin the block header such that proper blockchain construction (namely,trust) is self-verifiable. Without intending to be limiting, adistributed verifiable random function (DVRF) may be used to facilitatethe mining proof. Alternative approaches include use ofhardware-generated trusted random numbers.

Enabling Technologies

As noted above, the techniques of this disclosure may be implementedwithin the context of an overlay network, such as a content deliverynetwork (CDN), although this is not a limitation. In a known system ofthis type, such as shown in FIG. 9, a distributed computer system 100 isconfigured as a content delivery network (CDN) and is assumed to have aset of machines 102 a-n distributed around the Internet. Typically, mostof the machines are servers located near the edge of the Internet, i.e.,at or adjacent end user access networks. A network operations commandcenter (NOCC) 104 manages operations of the various machines in thesystem. Third party sites, such as web site 106, offload delivery ofcontent (e.g., HTML, embedded page objects, streaming media, softwaredownloads, and the like) to the distributed computer system 100 and, inparticular, to “edge” servers. Typically, content providers offloadtheir content delivery by aliasing (e.g., by a DNS CNAME) given contentprovider domains or sub-domains to domains that are managed by theservice provider's authoritative domain name service. End users thatdesire the content are directed to the distributed computer system toobtain that content more reliably and efficiently. Although not shown indetail, the distributed computer system may also include otherinfrastructure, such as a distributed data collection system 108 thatcollects usage and other data from the edge servers, aggregates thatdata across a region or set of regions, and passes that data to otherback-end systems 110, 112, 114 and 116 to facilitate monitoring,logging, alerts, billing, management and other operational andadministrative functions. Distributed network agents 118 monitor thenetwork as well as the server loads and provide network, traffic andload data to a DNS query handling mechanism 115, which is authoritativefor content domains being managed by the CDN. A distributed datatransport mechanism 120 may be used to distribute control information(e.g., metadata to manage content, to facilitate load balancing, and thelike) to the edge servers.

As illustrated in FIG. 10, a given machine 200 comprises commodityhardware (e.g., an Intel Pentium processor) 202 running an operatingsystem kernel (such as Linux or variant) 204 that supports one or moreapplications 206 a-n. To facilitate content delivery services, forexample, given machines typically run a set of applications, such as anHTTP proxy 207 (sometimes referred to as a “global host” process), aname server 208, a local monitoring process 210, a distributed datacollection process 212, and the like. For streaming media, the machinetypically includes one or more media servers as required by thesupported media formats.

A CDN edge server is configured to provide one or more extended contentdelivery features, preferably on a domain-specific, customer-specificbasis, preferably using configuration files that are distributed to theedge servers using a configuration system. A given configuration filepreferably is XML-based and includes a set of content handling rules anddirectives that facilitate one or more advanced content handlingfeatures. The configuration file may be delivered to the CDN edge servervia the data transport mechanism. U.S. Pat. No. 7,111,057 illustrates auseful infrastructure for delivering and managing edge server contentcontrol information, and this and other edge server control informationcan be provisioned by the CDN service provider itself, or (via anextranet or the like) the content provider customer who operates theorigin server.

The CDN may include a storage subsystem, such as described in U.S. Pat.No. 7,472,178, the disclosure of which is incorporated herein byreference.

The CDN may operate a server cache hierarchy to provide intermediatecaching of customer content; one such cache hierarchy subsystem isdescribed in U.S. Pat. No. 7,376,716, the disclosure of which isincorporated herein by reference.

The CDN may provide secure content delivery among a client browser, edgeserver and customer origin server in the manner described in U.S.Publication No. 20040093419. The approach described there is sometimesreferred to as an SSL-protected edge network. In a typical operatingscenario, secure content delivery enforces SSL-based links between theclient and the edge server process, on the one hand, and between theedge server process and an origin server process, on the other hand.This enables an SSL-protected web page and/or components thereof to bedelivered via the edge server. To enhance security, the service providermay provide additional security associated with the edge servers. Thismay include operating secure edge regions comprising edge serverslocated in locked cages that are monitored by security cameras,providing a key management service, and the like. In one embodimenthere, wallet services may be located in front of or behind anSSL-protected edge network.

In a typical operation, a content provider identifies a content providerdomain or sub-domain that it desires to have served by the CDN. The CDNservice provider associates (e.g., via a canonical name, or CNAME) thecontent provider domain with an edge network (CDN) hostname, and the CDNprovider then provides that edge network hostname to the contentprovider. When a DNS query to the content provider domain or sub-domainis received at the content provider's domain name servers, those serversrespond by returning the edge network hostname. The edge networkhostname points to the CDN, and that edge network hostname is thenresolved through the CDN name service. To that end, the CDN name servicereturns one or more IP addresses. The requesting client browser thenmakes a content request (e.g., via HTTP or HTTPS) to an edge serverassociated with the IP address. The request includes a host header thatincludes the original content provider domain or sub-domain. Uponreceipt of the request with the host header, the edge server checks itsconfiguration file to determine whether the content domain or sub-domainrequested is actually being handled by the CDN. If so, the edge serverapplies its content handling rules and directives for that domain orsub-domain as specified in the configuration. These content handlingrules and directives may be located within an XML-based “metadata”configuration file.

The above-described client-to-edge server mapping technique may be usedto associate a wallet or wallet service (the “client”) with an edgeserver. In a typical use case, a transaction initiated from or otherwiseassociated with that wallet or wallet service then passes through theedge server and onward to the core for further processing as describedherein. As noted above, the wallet or wallet service (or some portionthereof) may also reside inside the edge, such that wallet requests passthrough the edge to the wallet or wallet service and onward to the core.Some portion of the transaction processing may be carried out at theedge server.

Each above-described process preferably is implemented in computersoftware as a set. of program instructions executable in one or moreprocessors, as a special-purpose machine.

Representative machines on which the subject matter herein is providedmay be Intel hardware processor-based computers running a Linux orLinux-variant operating system and one or more applications to carry outthe described functionality. One or more of the processes describedabove are implemented as computer programs, namely, as a set of computerinstructions, for performing the functionality described.

While the above describes a particular order of operations performed bycertain embodiments of the invention, it should be understood that suchorder is exemplary, as alternative embodiments may perform theoperations in a different order, combine certain operations, overlapcertain operations, or the like. References in the specification to agiven embodiment indicate that the embodiment described may include aparticular feature, structure, or characteristic, but every embodimentmay not necessarily include the particular feature, structure, orcharacteristic.

While the disclosed subject matter has been described in the context ofa method or process, the subject matter also relates to apparatus forperforming the operations herein. This apparatus may be a particularmachine that is specially constructed for the required purposes, or itmay comprise a computer otherwise selectively activated or reconfiguredby a computer program stored in the computer. Such a computer programmay be stored in a computer readable storage medium, such as, but is notlimited to, any type of disk including an optical disk, a CD-ROM, and amagnetic-optical disk, a read-only memory (ROM), a random access memory(RAM), a magnetic or optical card, or any type of media suitable forstoring electronic instructions, and each coupled to a computer systembus. A given implementation of the present invention is software writtenin a given programming language that runs in conjunction with aDNS-compliant name server (e.g., BIND) on a standard Intel hardwareplatform running an operating system such as Linux. The functionalitymay be built into the name server code, or it may be executed as anadjunct to that code. A machine implementing the techniques hereincomprises a processor, computer memory holding instructions that areexecuted by the processor to perform the above-described methods.

While given components of the system have been described separately, oneof ordinary skill will appreciate that some of the functions may becombined or shared in given instructions, program sequences, codeportions, and the like.

While given components of the system have been described separately, oneof ordinary skill will appreciate that some of the functions may becombined or shared in given instructions, program sequences, codeportions, and the like. Any application or functionality describedherein may be implemented as native code, by providing hooks intoanother application, by facilitating use of the mechanism as a plug-in,by linking to the mechanism, and the like.

The techniques herein generally provide for the above-describedimprovements to a technology or technical field, as well as the specifictechnological improvements to various fields.

Each above-described process preferably is implemented in computersoftware as a set of program instructions executable in one or moreprocessors, as a special-purpose machine.

The edge network may communicate with the core using varioustechnologies. Representative overlay network technologies that may beleveraged include those described in U.S. Publication Nos. 2015/0188943and 2017/0195161, the disclosures of which are incorporated herein byreference. Among other things, these publications describe the CDNresources being used facilitate wide area network (WAN) accelerationservices over the overlay in general, as well as between enterprise datacenters (which may be privately-managed) and third partysoftware-as-a-service (SaaS) providers. In one typical scenario, aso-called routing overlay leverages existing content delivery network(CDN) infrastructure to provide significant performance enhancements forany application that uses Internet Protocol (IP) as a transport protocolby routing around down links or finding a path with a smallest latency.Another approach is to provide messages from the edge to the core usingmulticast, unicast, broadcast or other packet-forwarding techniques.

The techniques herein generally provide for the above-describedimprovements to a technology or technical field, as well as the specifictechnological improvements to various fields including distributednetworking, distributed transaction processing, wide areanetwork-accessible transaction processing systems, high performance, lowlatency transaction processing systems, non-blocking full meshinterconnect systems, and the like, all as described above.

Having described the subject matter, what is claimed is as follows.

1. A method, performed in association with a transaction processingsystem comprising a set of transaction handlers that receive and processmessages into a blockchain, wherein a message is associated with atransaction to be included in the blockchain, wherein the transactionhas associated therewith a set of one or more Unspent TransactionOutputs (UTXOs), comprising: providing an Unspent Transaction Output(UTXO) handling layer distinct from the set of transaction handlers, theUTXO handling layer comprising a set of UTXO handlers; wherein duringprocessing of a given segment of a block in the blockchain, a giventransaction handler in the set of transaction handlers interacts with arespective UTXO handler using a transaction handler-provider handleuniquely associated with a request to the UTXO handler; and using thetransaction handler-provided handle, selectively undoing at least oneoperation associated with a transaction.
 2. The method as described inclaim 1 wherein the at least one operation is an operation that hassucceeded.
 3. The method as described in claim 1 wherein the at leastone operation is an operation that has timed-out.
 4. The method asdescribed in claim 1 wherein the at least one operation is undonefollowing a collision in the use of first and second UTXOs.
 5. Adistributed computing system, comprising: a set of transaction handlingcomputing elements that receive and process messages into a blockchain,wherein a message is associated with a transaction to be included in theblockchain, wherein a transaction has associated therewith a set of oneor more Unspent Transaction Outputs (UTXOs); at least one UTXO handlerthat is distinct from the set of transaction handling computingelements; and a lock-free distributed UTXO database supported across theset of transaction handling computing elements; wherein the at least oneUTXO handler detects collisions in the use of UTXOs and, in responsethereto, reverses a transaction associated therewith; wherein thetransaction handling computing elements and the UTXO handler eachexecute as software in a hardware processor.
 6. The distributedcomputing system as described in claim 5 wherein the at least one UTXOhandler is configured to enabling a UTXO to be spent only after the UTXOhas been mined into a previous block of the blockchain.
 7. Thedistributed computing system as described in claim 5 wherein the atleast one UTXO handler is one of set of UTXO handlers, and wherein aUTXO space is partitioned across the set of UTXO handlers.
 8. Thedistributed computing system as described in claim 5 wherein the atleast least one UTXO handler interacts with a particular transactionhandling computing element using a transaction handler-provider handleuniquely associated with a request to the UTXO handler.
 9. Thedistributed computing system as described in claim 8 wherein the UTXOhandler reverses the transaction using the transaction handler-providedhandle.